The rebuild kits are available from reliable Cruiser vendors, as well as RockAuto. There is a difference in kits between front axle and rear, and when removing and reinstalling the individual wheel cylinders the specific orientation matters (front left wheel, forward cylinder vs. rear, etc.). This is to correctly position the star wheel adjusters to rotate when manipulated with a drum brake tool through the service hole.
Rebuilding all eight is straightforward and simple, but does take some time if you want to clean them up a bit and paint them before reinstalling. The biggest obstacle will be if your star wheel adjusting screws are rusted and/or seized - that was my biggest hurdle. When reassembling and installing, use anti-seize on all threads and mating surfaces.
Since rebuilding all eight of mine, with new shoes and drums properly bled and adjusted, I can stop on a dime and stand the truck on its' nose.
Good luck!
Brian